1. Field of the Invention
The present invention relates to a push button circuit breaker switch and in particular, relates to a switch employing an alloy metal which deforms while its temperature rises to a specific point. A circuit is closed or opened automatically when the current via the switch has exceeds a predetermined current value.
2. Description of the Prior Art
FIG. 1 shows an exploded view of a prior art push button switch. When the push button 1 is at the top position of a housing before it is depressed, the contact 206 of a conductive plate 204 and the contact 210 of the connecting leg 208 are separated from each other. When the push button 202 is depressed, the protruded rod 212 of the push button 1 triggers the conductive plate 204 such that the contact 206 contacts with the contact 210.
Thus, the switch is shifted to a conductively connected state. However, this switch provides only the function of ON and OFF, it can not automatically cut off the circuit at a specified current value. As there is no automatic current breaking device in the switch, manual operation is required to shift from ON or OFF state. In order to automatically cut off the current supply to the circuit, there are different kinds of fuse devices available. However, it is not convenient to replace a fuse when it melts. Further, it is necessary to keep a number of fuses in stock for ready use.
In other conventional art, a safety device is employed after the circuit is opened such that by depressing a button thereof, the switch can be restored and ready to use. However, in this prior art, the circuit is very complicated as an additional safety device has to be installed. It is not economical due to greater costs of material, installation and fabrication.
U.S. Pat. No. 5,786,742 relates to a push button switch with an override interruption structure. Referring to FIGS. 1, 2 and 4 to 8 of the patent, the switch comprises a push button 1 connected to contacts 61, 62. When the push button 1 is depressed, the contacts 61, 62 respectively contact with the contacts 731 and 461 of a first conductive plate 73 and a second conductive plate 46 such that the switch is switched to the ON state. This switch employs a well-known mechanism such that when the button 1 is depressed, it remains in the pressed-down position, and the button 1 restores to its original position to open the circuit when the button 1 is depressed once again. In addition, the switch comprises a circuit cut-off device, and when the alloy 75 is overheated, it deforms and causes the push button 1 to be released. Thus the push button 1 restores to its original position, and the contacts are separated. The switch is changed from the ON state to the OFF state.
The present invention relates to a push button circuit breaker switch which comprises a housing having an opening; a push button fitted to the opening within the housing; a press rod being mounted below the push button and being moveable vertically, and including a contacting rod; a spring being mounted under the press rod, such that the press rod displaces downwards to urge said spring; a conductive plate mounted at the housing and having a resilient plate with a contact, such that the press rod displaces downwards to compress said resilient plate; a first conductive terminal positioned at the housing and having a connecting leg end and a contact, the connecting leg end being protruded out of the housing such that the compression of the resilient plate of the conductive plate causes the contact thereof to contact with the contact of the first conductive terminal; an alloy metal having one end being secured to the conductive plate and having a contact at the other end; a second conductive terminal being secured to the housing and having a connecting leg end and a contact, the connecting leg end being protruded out of the housing, the contact being connected to the contact of the alloy metal before the alloy metal is heated and deformed; an insulating plate having an insulating end and being mounted with a compression spring; a triangular passage being mounted at the housing; an interlinking rod having one end pivotally mounted at the press rod and having the other end being connected to the passage; whereby the pushing of said push button changes the switch from xe2x80x9cOFFxe2x80x9d position to the xe2x80x9cONxe2x80x9d position, and when the current passed through the switch has exceeded a predetermined current value, the alloy metal curves at that instance and the contact of the alloy metal disengage from the contact of the second conductive terminal, and as a result of the force of the spring, the insulating end of the insulating plate moves into the gap formed between the two contacts, a second push on the push button resets the switch to OFF position.
Another object of the present invention is to provide a push button circuit breaker switch, which is reliable and inexpensive to manufacture.
Yet another object of the present invention is to provide a push button circuit breaker switch which can automatically switch off the current supply.